Coated separator with compressible elasticity, thermal shutdown and high temperature resistance

Patent metadata

Field	Value
Publication number	US-10084169-B2
Application number	US-201114443391-A
Country	US
Kind code	B2
Filing date	Nov 1, 2011
Priority date	Sep 30, 2011
Publication date	Sep 25, 2018
Grant date	Sep 25, 2018

Abstract

A lithium ion battery separator consists of a PE micro-porous substrate A and a micro-porous coating B which is located on the substrate A and formed of mixing pre-crosslinked rubber particles and ceramic fine powder composite materials. The separator has characteristics of good compressible elasticity, thermal shutdown, low heat shrinkage, high temperature membrane rupture resistance and so on.

First claim

The invention claimed is:

1. A coated membrane, the coated membrane comprising:
at least a composite material-based microporous coating comprising a first coating side; and
a PE-based microporous substrate comprising a first substrate side and a second substrate side;

wherein:
the PE-based microporous substrate is mainly composed of high density polyethylene, and has a porosity of between 35 and 80%, a longitudinal tensile strength of more than 70 megapascal, and a transverse elongation at break of more than 100%;
an average pore size of the first substrate side is between 100 and 800 nm, and the average pore size of the first substrate side is larger than that of the second substrate side;
the composite material-based microporous coating has a thickness T b of between 3 and 25 μm, and comprises pre-crosslinked rubber particles with a gel content exceeding 35%, ceramic micropowders with a room temperature resistivity exceeding 10 12 Ω·cm, and a water-soluble polymer binder;
the pre-crosslinked rubber particles account for between 15 and 60 wt. % of three components of the composite material-based microporous coating;
an average particle size of the pre-crosslinked rubber particles is between 100 and 800 nm, and an average particle size of the ceramic micropowders is between 200 and 800 nm;
the first coating side is coated on the first substrate side;
the coated membrane has the following characteristics:
(1) compressible elasticity: a total thickness T ab of the coated membrane is between 12 and 50 μm; at a temperature of between 45 and 60° C., when exerting a static compressive stress of 50 pounds per square inch (PSi) on the coated membrane for one hour along a thickness direction thereof, a compression deformation of the coated membrane along the thickness direction is greater than 10% of the Tab and less than 30% of the T ab ; 15 min later upon release of pressure, the thickness restores to more than 93% of an original thickness prior to compression; and after 500 cycles, the thickness restores to still more than 90% of the T ab ; and
(2) thermal shutdown and high temperature resistance: when exerting a static compressive stress of 1 PSi on the coated membrane along the thickness direction thereof, and heating the coated membrane with a rate of 1° C./min from 100° C. to 200° C., a thermal shutdown temperature of the coated membrane is between 125 and 145° C.; when maintaining the temperature of 200° C. for 15 min, and cooling the coated membrane to room temperature, physical appearance of the coated membrane keeps intact, a longitudinal and transverse thermal shrinkage is less than 5%, and a Gurley value increases to exceed 2000 S/100 CC; and

the ceramic micropowders are hexagonal boron nitride powders having a Mohs Hardness of less than 4, a thermal conductivity of more than 30 w/m·k, and a room temperature resistivity of more than 10 13 Ω·cm.

2. The coated membrane of claim 1 , wherein an original Gurley value of the coated membrane is between 50 and 500 S/100 CC, a breakdown voltage thereof is greater than 300 V, and a peeling strength thereof is greater than 20 gf/cm.

3. The coated membrane of claim 1 , wherein the pre-crosslinked rubber particles employ rubber latex as a raw material, and the rubber latex is irradiated and crosslinked under an irradiation dose of between 30 and 300 KGy; a glass transition temperature of the rubber particles is below minus 25° C.; irradiated rubber latex is, free from drying, directly mixed in an emulsion state with the ceramic micropowders and the water-soluble polymer binder, and then dispersed uniformly; the rubber latex is selected from the group consisting of carboxylic styrene butadiene rubber (XSBR), carboxylic acrylonitrile butadiene rubber (XNBR), carboxylic polybutadiene rubber (XBR), butadiene-styrene-vinyl pyridine rubber (PSBR), vinyl pyridine-butadiene rubber (PBR), ethylene-propylene methylene copolymer (EPM), styrene butadiene rubber (SBR), polyisobutylene (PIB), ethylene propylene diene rubber (EPDM), isobutylene-isoprene rubber (IIR), isoprene rubber (IR), styrene-isoprene-butadiene rubber (SIBR), nitrile butadiene rubber (NBR), butadiene rubber (BR), acrylate rubber, silicone rubber, fluororubber, and a combination thereof.

4. The coated membrane of claim 1 , wherein the ceramic micropowders comprise an oxide or nitride of an element selected from Al, Si, Zr, Mg, Ti, and B.

5. The coated membrane of claim 1 , wherein the water-soluble polymer binder has a weight average molecular weight of more than 50,000, and is selected from the group consisting of carboxymethyl cellulose (CMC), polyvinyl pyrrolidone (PVP), polyoxyethylene, polyvinyl alcohol, an adduct of polypropylene glycol and ethylene oxide, and a combination thereof; the water-soluble polymer binder accounts for between 0.5 and 8 wt. % of the three components of the composite material-based microporous coating, particularly between 1 and 5 wt. %.

6. The coated membrane of claim 1 , wherein the pre-crosslinked rubber particles, the ceramic micropowders, and the water-soluble polymer binder are mixed to yield an aqueous slurry, to which a non-ionic surface active agent accounting for 0-1 wt. % of the aqueous slurry is added prior to coating; the non-ionic surface active agent is selected from the group consisting of nonylphenol polyoxyethylene ether, octaphenyl polyoxyethyiene, high carbon (C 12-22 ) fatty alcohol polyoxyethylene ether, an adduct of polypropylene glycol and ethylene oxide, a non-ionic fluorocarbon surfactant, and a combination thereof.

7. The coated membrane of claim 1 , wherein the pre-crosslinked rubber particles, the ceramic micropowders, and the water-soluble polymer binder are mixed to yield an aqueous slurry, and a second solvent which is mixed with water and then wetted with polyethylene is added to the aqueous slurry prior to coating, a weight ratio of the aqueous slurry to the second solvent being between 100:0 and 100:50; the second slurry is selected from the group consisting of isopropanol, butanol, N-methylpyrrolidone, N-ethylpyrrolidone, N-octylpyrrolidone, polyethylene glycol and polypropylene glycol having a molecular weight of between 200 and 800, and a combination thereof.

8. The coated membrane of claim 1 , wherein the PE-based microporous substrate comprises two layers of microporous membrane, a first layer is a polypropylene microporous membrane, and a second layer is a PE-based microporous membrane.

9. A lithium ion battery, comprising the coated membrane of any one of preceding claims 1 - 8 , wherein the composite material-based microporous coating further comprises a second coating side, and the second coating side contacts a negative pole piece of the battery.

10. The coated membrane of claim 1 , wherein an average pore size of the second substrate side is between 50 and 150 nm.

Assignees

• Li Xin
• Li Jianhua
• Chen Wei
• Jiao Yongjun
• Li Long
• Deng Xinjian
• Tianjin Dg Membrane Co Ltd

Inventors

• Li Xin
• Li Jianhua
• Chen Wei
• Jiao Yongjun
• Li Long
• Deng Xinjian

Classifications

• H01M10/4235 Primary

  Safety or regulating additives or arrangements in electrodes, separators or electrolyte (H01M10/4242 takes precedence) · CPC title

• H01M50/417

  Polyolefins · CPC title

• H01M50/491

  Porosity · CPC title

• H01M50/489

  Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties · CPC title

• H01M50/449

  having a layered structure · CPC title